Specifications

TRUE
and MAGNETIC POSITION
Most
navigators
realize there is a difference between true and
mag-
netic north. True north is the
top
of the world. It's where all lines of
longitude converge. Magnetic
north is the location our
compasses
point.
It lies several hundred
miles to the south of true
north,
at a
location in
Canada.
Charts are
usually
laid out
according
to a Mercator
projection
which
uses true north.
If
you plot
a course on a chart
using
the Mercator
projection, you'll
either have to convert
magnetic readings
to true or
use true
readings.
The UltraNav can
display navigation
information in
magnetic
or true.
When it's turned on for the
very
first
time, magnetic
is used. To
switch to
true,
press
the MENU
key,
then
press
the
key adjacent
to
the "CHANGE SETUP" label. Now
press
the
key adjacent
to the
"MORE" label two times. The menu shown below
appears.
In this
example,
magnetic
is in effect. Press the
key adjacent
to the "SE-
LECT TRUE BEARING"
label. The screen will clear and
return
to the
last used
loran
screen, showing
all
navigation
information
in
degrees
true.
Repeat
these
steps
to switch back to
magnetic.
The menu that
originally
said "SELECT TRUE BEARING" now reads "SELECT
MAGNETIC BEARING".
POSITION DISPLAY
The
position display
shows
your
present position, heading, speed
over
ground, depth,
and status
displays.
The GRI in use and the mode
(auto-
matic or
manual) display
at the
top
of
the screen.
Immediately
beneath
these is the
present position
display.
It shows
your present position
in either
latitude/longitude
or TD's. To the left
of the word "POSITION" is the ASF
indicator. It
only
shows when ASF's
are in use. On the far
right
is the
primary/alternate
solution
display.
If
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the unit is in the
primary mode,
the letters "PAl"
appear.
"ALT"
appear
if the unit is in the alternate mode. In this same areais the fix
quality
indicator. Fix
quality
is a measure of the
lines
of
position's
crossing angles.
If the fix.
quality
is
poor,
use the
displayed
informa-
tion with caution. The
displayed position
can
and
will
vary
with
poor
crossing angles.
The
position display
flashes the last known
position
when the fix
quality
is not usable. A number
to the
right
of the
fix
quality message
shows the fix
quality's
value, It's
range
is from zero
(0)
to
nine
(9),
with zero the worst and nine the best.
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Remember,
do not use the loran for
navigation
when the
position
display
flashes. Find and
correct the
problem
before
navigating
with
the
unit.
Beneath the
fix
quality message
is
your heading,
or direction the boat
is
travelling. Speed
over
ground (SOG)
shows
your
actual
speed,
regardless
of the
speedometer reading.
For
example,
if
you're
trav-
elling
at ten knots
directly against
a two knot
current,
then
your speed
over
ground
is
eight
knots. You will
typically
need to travel some
distance in a
straight
line before the SOG feature
"settles down" and
gives
an accurate
reading.
The last.
display
on this screen is the
digital depth display.
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